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April
2002
Volume 66 |
Number
4
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WHAT'S
NEW
Therapy of PONV: An Overview |
Ashish
C. Sinha, M.D., Ph.D.
Patients preparing
for surgery frequently express three fears: not waking up after
surgery, waking up during surgery and throwing up after surgery.
As anesthesiologists we can reassure them about the first, be
vigilant against the second and work toward alleviation of the
third. The overall incidence of postoperative nausea and vomiting
(PONV) is estimated at between one-in-four to one-in-three patients,
although this varies considerably from practice to practice, depending
upon factors such as types of case (e.g., pediatric or endoscopic),
routine prophylactic use of antiemetics and, frequently, time
to follow-up. Overall, the PONV odds may vary from three-out-of-five
to one-in-20. In our institution, with no obstetric or trauma
cases and very few pediatric cases, our incidence of PONV is around
5 percent. As a group, we also are very aggressive about treating
PONV preoperatively, intraoperatively and postoperatively.
The etiology
and consequences of PONV are complex as well as multifactorial,
involving patient, medical problems, surgery and anesthetic technique.
The treatment of PONV has at different times involved the use
of anticholinergics, phenothiazines, antihistamines, butyrophenones
and benzamides. Newer pharmacotherapy of PONV involves serotonin
receptor antagonists, steroids and, just over the horizon maybe,
NK-1 receptor antagonists.
Traditionally,
patient factors that have been associated with increased incidence
of PONV have included female sex, young age, obesity, history
of motion sickness, history of gastroesophageal dysfunction, smoking,
anxiety and even difficult airway. Site of surgery involving the
head and neck, oropharynx, ears and eyes as well as intra-abdominal
procedures is similarly associated with increased PONV. Anesthetic
techniques also affect incidence, being increased by general anesthetic
(versus regional and local). With general anesthesia, narcotics
and nitrous oxide are more to blame than propofol. Similarly,
aggressive bag-mask ventilation or nonuse of an orogastric tube
can negatively impact incidence.
Obesity, or
more accurately, body mass index (BMI), would seem to be a risk
factor associated with increased PONV, but statistical studies
do not bear this out. Statistically, women on the 20th day of
their menstrual cycle have the lowest incidence of PONV; the highest
is on day five. Smoking, with its multitude of negative effects
on the cardiovascular and respiratory system, would appear to
be associated with higher incidence of PONV, but statistical studies
indicate quite the opposite.
Droperidol
(a butyrephenone, which is a dopaminergic antagonist), a very
popular antiemetic, has come under a cloud because of the recent
communication regarding increased QT intervals and dysrhythmias.
Even though this was reported at doses over 2 mg, it is likely
that use at the 0.625 mg level also will decrease. Droperidol
is known to unmask major anxiety in patients before surgery and
can cause extrapyramidal reactions, agitation and dysphoria. [See
related article about droperidol on page 19.]
Transdermal
scopolamine (1.5 mg) recently has become available for PONV, though
it has been used for the last 20 years for motion sickness. Even
though it is an inexpensive, long-lasting and effective method
of PONV treatment, one-third of the patients will suffer from
dry mouth and up to one-eighth from dizziness.
Propofol,
with its action on the cerebral cortex as well as its interactions
with dopaminergic and serotoninergic receptors, has become the
popular antiemetic anesthetic drug. Using propofol-ketamine in
room air for spontaneously breathing patients simulates the conditions
for general anesthesia and has a very low emetic potential.
Ondansetron
has been studied extensively as an agent used in PONV as an extension
of its use in chemotherapy-induced nausea and vomiting (CINV).
Its effectiveness in combating PONV is comparable to droperidol
without the cardiovascular or psychological side effects. Its
use is probably limited by cost factors more than anything else.
It is probably the most used rescue medication for PONV and, in
some places, the most used prophylactic antiemetic as well. Dolasetron,
the other major 5HT3 antagonist, had garnered support with its
financial argument over ondensetron since both have similar pharmacological
profiles and similar side effects, namely headache, dizziness
and diarrhea.
Dexamethasone
in a single dose of 5 or 10 mg appears to have no toxic effects
in otherwise healthy individuals while having a significant reduction
in late PONV. Possibly the best results may be obtained by combining
dexamethasone with a 5HT3 antagonist or droperidol.
Of all the
neurotransmitters implicated in triggering emesis, the tachykinin
substance P has been shown to play a key role in emetic responses
because of its location in the brain's emetic regions as well
as in the gastrointestinal vagal efferent. Substance P has been
shown to induce vomiting when administered intravenously to laboratory
animals. Substance P is postulated to be the endogenous ligand
for neurokinin1 (NK1) receptors, and NK1 receptor antagonists
have shown much promise as effective treatment in both CINV and
PONV.
Nonpharmacological
techniques used in management of PONV include acupuncture, acupressure,
electroacupuncture, acupoint stimulation and transcutaneous electrical
nerve stimulation. Use of acupuncture, acupressure and laser stimulation
of pericard 6 located near the wrist has been shown to be effective
prophylaxis of PONV. Interestingly, acupuncture offers no benefit
to children, possibly indicating that if you do not expect relief,
you will not find it. Acupuncture has been shown to be effective
not only in the treatment of CINV and PONV but also in headache,
low-back pain, alcoholism and even in paralysis secondary to stroke.
One gram of
ginger preoperatively has been shown to be more effective than
placebo in the treatment of PONV. Deep breathing, the first response
asked of by PACU nurses, along with a cool washcloth on the forehead,
may be more effective than we would like to believe. Deep inhalation
of vapors of alcohol, peppermint or even saline seem to decrease
nausea scores by 50 percent in less than five minutes.
Given all
this, is the goal of zero PONV achievable? Is it desirable? Is
it beneficial? Yes, yes and yes! Combining all the modalities
available to us, from propofol to ondansetron, from total intravenous
anesthesia to gentle reambulation, from not forcing the patient
to partake of oral fluids prior to discharge from the PACU, to
telling the transportation orderly to drive patient-friendly,
would all go a long way in decreasing the incidence of PONV in
our practice. Patients that pass through our hands in our care
and suffer no nausea or vomiting will thank us from the bottom
of their stomachs.
Bibliography:
Borgeat A, Stirnemann HR. Antiemetic effects of propofol [article
in German]. Anaesthesist. 1998; 47(11):918-924.
Culy CR, et
al. Ondansetron: A review of its use as an antiemetic in children.
Paediatr Drugs. 2001; 3(6):441-479.
Diemunsch
P, Grelot L. Potential of substance P antagonist as antiemetics.
Drugs. 2000; 60(3):533-546.
Eberhart LH,
et al. The menstruation cycle in the postoperative phase. Its
effect of the incidence of nausea and vomiting [article in German].
Anaesthesist. 2000; 49(6):532-536.
Ernest E,
Pittler MH. Efficacy of ginger for nausea and vomiting: A systematic
review of randomized clinical trials. Br J Anaesth. 2000; 84(3):367-371.
Friedberg
BL. Propofol-ketamine technique: Dissociative anesthesia for office
surgery. Anesthetic Plast Surg. 1999; 23(1):70-75.
Henzi I, et
al. Dexamethasone for the prevention of postoperative nausea and
vomiting: A quantitative systemic review. Anesth Analg. 2000;
90(1):186-194.
Kovac AL.
Prevention and treatment of postoperative nausea and vomiting.
Drugs. 2000; 59(2):213-243.
Kranke P,
Apefel CC, et al. An increased body mass index is no risk factor
for postoperative nausea and vomiting. Acta Anaesthesiol Scand.
2001; 45(2):160-166.
Lee A, Done
AL. The use of nonpharmacologic techniques to prevent postoperative
nausea and vomiting: A metaanalysis. Anesth Analg. 1999; 88(6):1362-1369.
Mayer DJ.
Acupuncture: An evidence-based review of the clinical literature.
Annu Rev Med. 2000; 51:49-63.
Rodrigo C.
The effect of cigarette smoking on anesthesia. Anesth Prog. 2000;
47(4):143-150.
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Ashish
C. Sinha, M.D., Ph.D., is Assistant Professor of Anesthesiology,
Department of Anesthesiology, University of Texas M.D. Anderson
Cancer Center, Houston, Texas. |
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